Dynamo-electric machine



Jan. 13. 1925. 1,523,034

R. E. DOHERTY DYNAMO ELECTRI C MACHINE Filed Nov 21, 1923 Inventor.-

Poberi' E. Doberg, 42

Patented Jan. 13, 1925.

UNITED STATES 1,523,004 PATENT, OFFICE.

ROBERT ERNEST DOHERTY, 0F SCOTIA, NEW YORK. ASSIGNOR TO GENERAL ELECTRIC i 4 COMPANY, A CORPORATION OF NEW YORK.

DYNAMO-ELECTRIC MACHINE.

Application filed November 21, 1823. Serial No. 676,151.

To all to from it may concern:

Be it known that I, ROBERT E. Donnn'rr, a citizen of the United States, residing at Scotia. in the county or" Schenectady, State of New York, have invented certain new andusetul Improvements in Dynamo-Electric hllachines, of which the following is a specification.

My invention relates to dynamo electric machines and particularly to such machines having commutated armature windings.

It is well known that the commutation of direct current dynamo electric machines can be greatly improved by providing them with commutating poles having windings which not only neutralize the armature reaction in the commutating zone, but also produce a commutating field. Even in such machines. however, commutation is often disturbed by stray magnetic fields in the commutating zone. In accordance with my invention I provide means for preventing these stray magnetic fields from entering the armature in the commutating zone.

Other features of novelty which charac' terize m invention are pointed out in the claims annexedto and forming a part of this specification. For a better understanding of my invention, reference may be had to the following description taken in connection with-the accompanying drawing, in which Fig. 1 is an end view partly in section of a dynamo electric machine embodying my invention and Fig. 2 is a diagram of connections of the machine of Fig. 1.

In the drawing. the dynamo electric machine has an armature 1 provided with a commutator 2. and a field frame 3 provided with main poles 4- and commutating poles 5. The main poles are provided with exciting windings 6 and the commutating poles are provided with commutating windings 7. A magnetic shield comprising magnetic members 8 located outside of the commutating winding on each commutating field pole is provided for preventing stray fields from entering the armature in the commutating zone.

The magnetic shield is shown as a U- shaped member having the ends of the U towards said armature, the legs of the U being formed by the members 8. The commutating poles comprise two legs 9 separated from one another with the commutating windings 7 mounted on each leg. The

field member is also provided with a com pensat-ing winding 10 comprising coils 11. 12, 13 and let located near the surface of the armature and about the ends of the legs 9 of the commutating poles and the legs 8 of the U-shaped member. Compensating windings may also be placed in the pole faces of the main poles 4 to prevent distortions of the main flux, as is usual in direct current machines.

In order to dampen out the flux tooth ripples and thus improve commutation, I preferably provide continuous non-magnetic members 22 between the commutating poles 5 and the armature 1. In the particular arrangement shown, these members are made of copper, are dish-shaped and hold in place the coils of the compensating winding 10.

The legs 9 of the commutating poles are connected together at their ends away from the armature by a magnetic member 15, which is in turn supported from the crossmember 16 of the magnetic shield by a non magnetic member 17.

In the diagram of connections, the supply mains 18 are shown as having connected across them the exciting windings 6, in the circuit of which is a regulating rheostat 19. One of the mains 18 is shown as connected to the positive brushes 2O bearing on the commutator 2 and the other main is shown as connected to the negative brushes 21, the commutating field winding 7 and the compensating field winding 10 being in series with this supply main.

The main poles 4 have a small pole are so that the neutral or compensating zone is a wide one. The compensating winding 10 is designed so as to neutralize the armature reaction and the commutating winding 7 is designed to produce a commutating field flux which flows out of one of the legs 9. through that portion of the armature in which the coil or coils undergoing commutation are located, back through the other leg of the same commutating pole, and thence through the magnetic member 15. Any stray field set up by the main poles 4, which would in the ordinarily constructed field member tend to enter the armature in the commutating zone under the commutating poles, is prevented by my construction and flows instead through the U-shaped magnetic shield, that is, through one of the f =l"" -L" 'l legs 8, {through the cross-member 16, through the other leg 8 of the same shield intothe nestadjacent ;1nain pole. By providing the non-Iriagne support 17 for the 5 commutating poles, tliere is no tendency for the path of the'commutating pole flux to be disturbed by this magnetic shield.

By my construction, avery wide neutral or cornmutating zone is produced, and if, for any reason the brushes are not set in exactly the middle. of the neutral one. or there is a shifting of the neutral zone with changes of load, sparkless commutation may still be obtained. H

I desirevit to be; understood that my in- .rention,is notlimited to the particular araangement; shown and described, andI aim ,inthe appended claims to cover all modifications which do not depart from the spirit "andscope of my invention.

hat I claim'as new and desire to secure by Letters Patentot the United States, is:

, l ln a dynamo ,armature provided electric machine, an with a commutator, ,main fieldgpoles having exciting windings th e commutating windings thereon, and means for preventing stray magnetic fields from entering said armature in the commutating 9 zone I I 2 ,111 aldynamo electric machine, an ar- 'j, .mature,provided with a commutator, main Qfieldlpoleshaving exciting-windings there-' on, commutating fieldfpoles having commutating windings thereon, and a magnetic shield for ,e aclr of said commutating field ,poles for-gpieveiitiiig stray magnetic fields trom entering said armature in the commutating Zone, M r 3.I In.a dynamo electric machine, an arimature provided with a commutator, main field poles having exciting windings thereon;commutating field poles having com- Imutating., windings thereon, and magnetic members located outside said commutating w,indii 1g. on each lot said oomlnutating field, olesjand acting .asa shield for prerent rig stray [ma'gntio fields from entering saidsarjmature the commuta ting Zone.

mature. ,provided with: a] commutator, main field poles having exciting windings there on, Icommutating ,field poles having commutatihg windings thereon, and a U shaned magnetic member folfleach of said comunutatingfield poles having the ends of the z toward. said armature, the legs of said U-shaped memberlbei'ng'located outside of f t-he said commutat'ing winding and acting as a shield for prev'ehting s'tray magnetic filClS frQljn entering {said armature' in the oommutat ng zone. v

a dynamo electr cmachme, an arnature sp Vided wltha commutator, 1119.111.

field poles having exciting windings therecommutating field poles having on, dominate-15 field poles, each of said commutating field poles comprising two legs's'eparated from one another, commutating field windings thereon, and "ina'gi'ietic niei'fibers located outside of'said commutating windings on each of said commutating -fic'ld'poles and acting as a shield for preventing stray magnetic fields from entering "minimum-e in'the commutating zone.

6. In a dynamo electric machine, an armature provided with a commutator, main field poles having exciting windings thereon, comniutating field poles, each of said coim'nutating'field poles comprising twolegs separatedfrom one another, commutating field windings thereon, magneticmembers loeated outside of said commutating wihdings on eachof said comin'utating field poles and acting as a shield-tor preventing st1'a v-;m'agneti c fields from entering said armature in the commutating Zone, and compensating windings located near the surface of said armature and about the ends 'ot' said legs of said 'commutating field poles and theends of said magnetic members. v In a dynamo electric machine, an armature providedwith a commutator, main field fpoles having; exciting windings thereon, "commutating field: poles, each of said commutating [field poles comprising two legs separated'trom one another, 'commutat ingl eld \i'in'dings thereon, and a lJ-shaped magnetic member for each of said commutatingfield polesha'ving the ends of the :U tmvard'said armature. the legs of said L l-shaped member heing located outside of said ,cominiitating'windings and acting as shield "for 2 preventing stray magnetic fields tijoin entering said'armature in the commutating zone. I V

Inf a dynamo;electric machine, an armature provided with a commutator, main fieldpolcs havingje xciting windings thereon, coinmi 'tatihg field poles, each of said commu tating field poles comprisingtwo legs eparated "from one andthen' commutating field windings: thereon, a 'U-sha'pedfmagirate member tor eaclroft said commutating having the ends of the U. toward entering armature in the commutating zone, and compensating windings located neair the surface of's aid armature and about the ends of said legs of said conimutating field poles and said legs of said U shaped member. I V V In a dynamd lectric machine.- an far-mature provided with a commutator, main field poles" having exciting windings thereon, commutatingfield poles, each of sale 'ck'imm'utatingfield'poles comprising two legs separated fiiom one an'other,-n0n magnetic supports for said connnutating field poles, commutating field windings thereon, and magnetic members located outside of said commutating windings on each side of said commutating field poles and acting as a shield for preventing stray magnetic fields from entering said armature in the commutating zone.

10111 a dynamo electric machine, an armature provided with a commutator, main field poles having exciting windings thereon, commutating field poles, each of said connnutating field poles comprising two legs separated from one another, nonmagnetic supports for said commutating field poles, connnutating field windings thereon, magnetic members located outside of said comlnutating windings on each of said comnmtating field poles and acting as a shield for preventing stray magnetic fields from enteringsaid armature in the commutating zone, and co-n'ipensating windings located near the surface of said armature and about the ends of said legs of said commutating field poles and the ends of said magnetic members.

11. In a dynamo electric machine, an armature provided with a commutator, main field poles having windings thereon, commutating field poles, each of said commutat-ing field poles comprising two legs separated from one another, non-magnetic supports for said commutating field poles, connnutating field windings thereon, and a U-shaped magnetic member for each of said commutating field poles having the ends of the U toward said armature, the legs of said thereon, commutating field poles, each of said connnutating field poles comprising two legs separated from one another, nonmagnetic supports tor said commutating field poles. commutating field windings thereon, a U-shaped magnetic member for each of said commutating field poles having the ends of the U toward said armature, the legs of said U-shaped member being located outside of said commutating windings and acting as a shield for preventing stray magnetic fields from entering said armature in the commutating zone, and compensating windings located near the surface of said armature and about the ends of said legs of said commutating field poles and said legs of said U-shaped member.

13. In a dynamo electric machine, an armature provided with a commutator, main field poles having exciting windings thereon, commutating field poles having commutating windings thereon, and continuous non-magnetic members between said commutating poles and said armature tor damping out the flux tooth ripples.

In witness whereof, I have hereunto set my hand this 20th day of November, 1923.

ROBERT ERNEST DOHERTY. 

